This invention relates to an underreamer apparatus, and more particularly to an underreamer apparatus having a substantial reduction in vertical height.
An underreamer is a device utilized in the drilled shaft industry to form a bell or enlargement at the bottom of a drilled shaft. Shafts are typically formed utilizing a drilling rig, which actuates an auger to form the cylindrical hole or shaft. After the shaft is completed, the underreamer with its doors in the retracted position is inserted into the shaft and lowered to the bottom. The drilling rig then actuates the underreamer by rotating the underreamer and partially extending the doors outwardly from the underreamer housing to begin excavation of the bell. After an amount of material is excavated, the doors of the underreamer are then retracted into the housing to collect and retain the excavated material within the housing. The underreamer is then raised to the surface to remove the excavated material from the drilled shaft and deposit the material on the surface. This process is repeated, such that each time the underreamer is lowered to the shaft bottom the underreamer doors are extended a greater amount to further enlarge the bell until the doors are fully extended having excavated the bell to its maximum diameter.
Heretofore, a frequently encountered problem in the use of underreamers relates to the fact that the devices are typically quite tall in relation to their diameter. The underreamer height has been necessary in order to accommodate the mechanism of the underreamer which functions to extend the underreamer doors and thereby provide the desired excavating function. The excessive height of the underreamer leads to difficulty in utilizing the device under obstructions, and the like.
The present invention comprises a novel underreamer apparatus which overcomes the disadvantages that have characterized the prior art. Thus, the preferred emobodiment of the invention comprises an underreamer apparatus which includes a toggle mechanism that substantially reduces the vertical height of an underreamer necessary to form an excavation of a given diameter.
In accordance with the aspects of the invention, an underreamer apparatus for belling out a portion of an underground hole into a conical configuration includes a vertically elongated housing having an upper and lower portion and a plurality of underreamer doors each including a toggle machanism.